Meta-Analysis of Genome-Wide Association Studies for Abdominal Aortic Aneurysm Identifies Four New Disease-Specific Risk Loci

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Rationale:

Abdominal aortic aneurysm (AAA) is a complex disease with both genetic and environmental risk factors. Together, 6 previously identified risk loci only explain a small proportion of the heritability of AAA.

Objective:

To identify additional AAA risk loci using data from all available genome-wide association studies.

Methods and Results:

Through a meta-analysis of 6 genome-wide association study data sets and a validation study totaling 10 204 cases and 107 766 controls, we identified 4 new AAA risk loci: 1q32.3 (SMYD2), 13q12.11 (LINC00540), 20q13.12 (near PCIF1/MMP9/ZNF335), and 21q22.2 (ERG). In various database searches, we observed no new associations between the lead AAA single nucleotide polymorphisms and coronary artery disease, blood pressure, lipids, or diabetes mellitus. Network analyses identified ERG, IL6R, and LDLR as modifiers of MMP9, with a direct interaction between ERG and MMP9.

Conclusions:

The 4 new risk loci for AAA seem to be specific for AAA compared with other cardiovascular diseases and related traits suggesting that traditional cardiovascular risk factor management may only have limited value in preventing the progression of aneurysmal disease.

XBP1 splicing triggers miR-150 transfer from smooth muscle cells to endothelial cells via extracellular vesicles

The interaction between endothelial cells (ECs) and smooth muscle cells (SMCs) plays a critical role in the maintenance of vessel wall homeostasis. The X-box binding protein 1 (XBP1) plays an important role in EC and SMC cellular functions. However, whether XBP1 is involved in EC-SMC interaction remains unclear. In this study, In vivo experiments with hindlimb ischemia models revealed that XBP1 deficiency in SMCs significantly attenuated angiogenesis in ischemic tissues, therefore retarded the foot blood perfusion recovery. In vitro studies indicated that either overexpression of the spliced XBP1 or treatment with platelet derived growth factor-BB up-regulated miR-150 expression and secretion via extracellular vesicles (EVs). The XBP1 splicing-mediated up-regulation of miR-150 might be due to increased stability. The SMC-derived EVs could trigger EC migration, which was abolished by miR-150 knockdown in SMCs, suggesting miR-150 is responsible for SMC-stimulated EC migration. The SMC-derived miR-150-containing EVs or premiR-150 transfection increased vascular endothelial growth factor (VEGF)-A mRNA and secretion in ECs. Both inhibitors SU5416 and LY294002 attenuated EVs-induced EC migration. This study demonstrates that XBP1 splicing in SMCs can control EC migration via SMC derived EVs-mediated miR-150 transfer and miR-150-driven VEGF-A/VEGFR/PI3K/Akt pathway activation, thereby modulating the maintenance of vessel wall homeostasis.

A Variant in LDLR Is Associated With Abdominal Aortic Aneurysm

Background—

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease among older people and demonstrates significant heritability. In contrast to similar complex diseases, relatively few genetic associations with AAA have been confirmed. We reanalyzed our genome-wide study and carried through to replication suggestive discovery associations at a lower level of significance.

Methods and Results—

A genome-wide association study was conducted using 1830 cases from the United Kingdom, New Zealand, and Australia with infrarenal aorta diameter ≥30 mm or ruptured AAA and 5435 unscreened controls from the 1958 Birth Cohort and National Blood Service cohort from the Wellcome Trust Case Control Consortium. Eight suggestive associations with P <1×10 −4 were carried through to in silico replication in 1292 AAA cases and 30 503 controls. One single-nucleotide polymorphism associated with P <0.05 after Bonferroni correction in the in silico study underwent further replication (706 AAA cases and 1063 controls from the United Kingdom, 507 AAA cases and 199 controls from Denmark, and 885 AAA cases and 1000 controls from New Zealand). Low-density lipoprotein receptor ( LDLR ) rs6511720 A was significantly associated overall and in 3 of 5 individual replication studies. The full study showed an association that reached genome-wide significance (odds ratio, 0.76; 95% confidence interval, 0.70–0.83; P =2.08×10 −10 ).

Conclusions—

LDLR rs6511720 is associated with AAA. This finding is consistent with established effects of this variant on coronary artery disease. Shared causal pathways with other cardiovascular diseases may present novel opportunities for preventative and therapeutic strategies for AAA.

Histone deacetylase 3 unconventional splicing mediates endothelial-to-mesenchymal transition through transforming growth factor β2

Histone deacetylase 3 (HDAC3) plays a critical role in the maintenance of endothelial integrity and other physiological processes. In this study, we demonstrated that HDAC3 undergoes unconventional splicing during stem cell differentiation. Four different splicing variants have been identified, designated as HD3α, -β, -γ, and -δ, respectively. HD3α was confirmed in stem cell differentiation by specific antibody against the sequences from intron 12. Immunofluorescence staining indicated that the HD3α isoform co-localized with CD31-positive or α-smooth muscle actin-positive cells at different developmental stages of mouse embryos. Overexpression of HD3α reprogrammed human aortic endothelial cells into mesenchymal cells featuring an endothelial-to-mesenchymal transition (EndMT) phenotype. HD3α directly interacts with HDAC3 and Akt1 and selectively activates transforming growth factor β2 (TGFβ2) secretion and cleavage. TGFβ2 functioned as an autocrine and/or paracrine EndMT factor. The HD3α-induced EndMT was both PI3K/Akt- and TGFβ2-dependent. This study provides the first evidence of the role of HDAC3 splicing in the maintenance of endothelial integrity.

Abstract 101: Reconstituted High-density Lipoprotein - More Than the Sum of Its Parts

Rationale

Reconstituted high-density lipoprotein (rHDL, CSL-111) particles have been shown to reduce multiple organ failure following hypovolemic shock, perturb irritable bowel syndrome and, more recently, to inhibit aneurysm formation in animal models. To identify new endothelial targets of the protective effect we examined the differential changes that occur in the proteome of activated primary endothelial cells following treatment with rHDLs.

Methods

Primary human endothelial cells were isolated from human umbilical cords, grown to confluence and activated with TNFα (10ng/ml), following a 4 hr incubation half the cells received rHDLs (1mg/ml, ApoAI) and the remaining cells received carrier only (10% sucrose). Protein lysates were prepared following 20 hr incubation and differential protein expression compared by scanning DiGE-2dimentional PAGE. Protein identities were confirmed using LC/MS of tryptic digests of proteins recovered from preparatory gels. Western blotting confirmed differential expression and established whether the response required the whole particle or solely the protein component of rHDLs.

Results

Of the proteins identified by LC/MS which were differentially expressed in response to rHDLs, Perilipin 3 (PLPN3, 1.3 fold, p<0.003); Growth factor receptor-bound protein 2 (GRB2, 2.5 fold, p<0.003) and Vimentin (1.6 fold, p<0.007) were induced, whilst sinexin 6 (SNX6, 1.2 fold p< 0.007); Glutathione S Transferase-1 (GST-1, 1.6 fold, p<0.02) and Crystallin-zeta like (CrystZL, 1.2 fold, p<0.004) were reduced. We found that the entire lipoprotein particle was necessary for the induction of PLN3 and reduction of SNX6. Concentration of rHDL < 100μg/ml were able to modulate the maximal effect observed. However, both rHDL and lipid free ApoAI were able to induce cytokine-inhibited expression of GRB2 (rHDL>ApoAI).

Conclusion

The PC component of rHDL is necessary for an acute effect on proteins involved in endosomal trafficking. Further studies are needed to understand the role this could play in the protective effect of HDL therapy.

Vascular endothelial cell growth-activated XBP1 splicing in endothelial cells is crucial for angiogenesis

BACKGROUND

Vascular endothelial cell growth factor plays a pivotal role in angiogenesis via regulating endothelial cell proliferation. The X-box binding protein 1 (XBP1) is believed to be a signal transducer in the endoplasmic reticulum stress response. It is unknown whether there is crosstalk between vascular endothelial cell growth factor signaling and XBP1 pathway.

METHODS AND RESULTS

We found that vascular endothelial cell growth factor induced the kinase insert domain receptor internalization and interaction through C-terminal domain with the unspliced XBP1 and the inositol requiring enzyme 1 α in the endoplasmic reticulum, leading to inositol requiring enzyme 1 α phosphorylation and XBP1 mRNA splicing, which was abolished by siRNA-mediated knockdown of kinase insert domain receptor. Spliced XBP1 regulated endothelial cell proliferation in a PI3K/Akt/GSK3β/β-catenin/E2F2-dependent manner and modulated the cell size increase in a PI3K/Akt/GSK3β/β-catenin/E2F2-independent manner. Knockdown of XBP1 or inositol requiring enzyme 1 α decreased endothelial cell proliferation via suppression of Akt/GSK3β phosphorylation, β-catenin nuclear translocation, and E2F2 expression. Endothelial cell-specific knockout of XBP1 (XBP1ecko) in mice retarded the retinal vasculogenesis in the first 2 postnatal weeks and impaired the angiogenesis triggered by ischemia. Reconstitution of XBP1 by Ad-XBP1s gene transfer significantly improved angiogenesis in ischemic tissue in XBP1ecko mice. Transplantation of bone marrow from wild-type o XBP1ecko mice could also slightly improve the foot blood reperfusion in ischemic XBP1ecko mice.

CONCLUSIONS

These results suggest that XBP1 can function via growth factor signaling pathways to regulate endothelial proliferation and angiogenesis.

XBP1 mRNA splicing triggers an autophagic response in endothelial cells through BECLIN-1 transcriptional activation

Sustained activation of X-box-binding protein 1 (XBP1) results in endothelial cell (EC) apoptosis and atherosclerosis development. The present study provides evidence that XBP1 mRNA splicing triggered an autophagic response in ECs by inducing autophagic vesicle formation and markers of autophagy BECLIN-1 and microtubule-associated protein 1 light chain 3β (LC3-βII). Endostatin activated autophagic gene expression through XBP1 mRNA splicing in an inositol-requiring enzyme 1α (IRE1α)-dependent manner. Knockdown of XBP1 or IRE1α by shRNA in ECs ablated endostatin-induced autophagosome formation. Importantly, data from arterial vessels from XBP1 EC conditional knock-out (XBP1eko) mice demonstrated that XBP1 deficiency in ECs reduced the basal level of LC3β expression and ablated response to endostatin. Chromatin immunoprecipitation assays further revealed that the spliced XBP1 isoform bound directly to the BECLIN-1 promoter at the region from nt -537 to -755. BECLIN-1 deficiency in ECs abolished the XBP1-induced autophagy response, whereas spliced XBP1 did not induce transcriptional activation of a truncated BECLIN-1 promoter. These results suggest that XBP1 mRNA splicing triggers an autophagic signal pathway through transcriptional regulation of BECLIN-1.

Galectin-9 protein expression in endothelial cells is positively regulated by histone deacetylase 3

Galectin-9 expression in endothelial cells can be induced in response to inflammation. However, the mechanism of its expression remains unclear. In this study, we found that interferon-γ (IFN-γ) induced galectin-9 expression in human endothelial cells in a time-dependent manner, which coincided with the activation of histone deacetylase (HDAC). When endothelial cells were treated with the HDAC3 inhibitor, apicidin, or shRNA-HDAC3 knockdown, IFN-γ-induced galectin-9 expression was abolished. Overexpression of HDAC3 induced the interaction between phosphoinositol 3-kinase (PI3K) and IFN response factor 3 (IRF3), leading to IRF3 phosphorylation, nuclear translocation, and galectin-9 expression. HDAC3 functioned as a scaffold protein for PI3K/IRF3 interaction. In addition to galectin-9 expression, IFN-γ also induced galectin-9 location onto plasma membrane, which was HDAC3-independent. Importantly, HDAC3 was essential for the constitutive transcription of PI3K and IRF3, which might be responsible for the basal level of galectin-9 expression. The phosphorylation of IRF3 was essential for galectin-9 expression. This study provides new evidence that HDAC3 regulates galectin-9 expression in endothelial cells via interaction with PI3K-IRF3 signal pathway.

Novel aspects of the pathogenesis of aneurysms of the abdominal aorta in humans

Aneurysm of the abdominal aorta (AAA) is a particular, specifically localized form of atherothrombosis, providing a unique human model of this disease. The pathogenesis of AAA is characterized by a breakdown of the extracellular matrix due to an excessive proteolytic activity, leading to potential arterial wall rupture. The roles of matrix metalloproteinases and plasmin generation in progression of AAA have been demonstrated both in animal models and in clinical studies. In the present review, we highlight recent studies addressing the role of the haemoglobin-rich, intraluminal thrombus and the adventitial response in the development of human AAA. The intraluminal thrombus exerts its pathogenic effect through platelet activation, fibrin formation, binding of plasminogen and its activators, and trapping of erythrocytes and neutrophils, leading to oxidative and proteolytic injury of the arterial wall. These events occur mainly at the intraluminal thrombus-circulating blood interface, and pathological mediators are conveyed outwards, where they promote matrix degradation of the arterial wall. In response, neo-angiogenesis, phagocytosis by mononuclear cells, and a shift from innate to adaptive immunity in the adventitia are observed. Abdominal aortic aneurysm thus represents an accessible spatiotemporal model of human atherothrombotic progression towards clinical events, the study of which should allow further understanding of its pathogenesis and the translation of pathogenic biological activities into diagnostic and therapeutic applications.

Proteomics and pitfalls in the search for potential biomarkers of abdominal aortic aneurysms

Proteomics is evolving as an important research technique in cardiovascular disease. We present exploratory research for a systemic biomarker of abdominal aortic aneurysm (AAA) in serum. Forty patients, 20 with large AAAs and 20 matched controls, were prospectively recruited. Serum was harvested, enriched, and mined for differential protein expression. Difference in gel electrophoresis using a two-dimensional platform, cyanine labeling, and Progenesis SameSpots software identified protein spots with significantly altered intensity. Liquid chromatography mass spectrometry aligned to the Seaquest protein database characterized proteins of interest, and 436 protein spots were demonstrated from the 20 processed gels. Thirteen spots of interest, demonstrating fold change (1.7-4) between the two patient cohorts and consistent significant differential expression (analysis of variance, p </= .003), were picked for identification. Four of 13 spots were identified according to their tandem mass spectra. These were fragments of serum albumin, hemoglobin, and apolipoprotein C-II precursor. Identified spots represented proteins highly abundant in serum, not candidate biomarkers. Issues of variability surrounding serum harvest, processing, enrichment, and the challenge of identifying minimally expressed proteins currently limit this avenue of research. No proteins identified in this study had the biologic plausibility to represent a possible biomarker of aneurysmal disease. The tissue proteome may be a more rewarding approach for preliminary investigation of plausible biomarkers.

Histone deacetylase 7 controls endothelial cell growth through modulation of beta-catenin

RATIONALE

Histone deacetylase (HDAC)7 is expressed in the early stages of embryonic development and may play a role in endothelial function.

OBJECTIVE

This study aimed to investigate the role of HDAC7 in endothelial cell (EC) proliferation and growth and the underlying mechanism.

METHODS AND RESULTS

Overexpression of HDAC7 by adenoviral gene transfer suppressed human umbilical vein endothelial cell (HUVEC) proliferation by preventing nuclear translocation of beta-catenin and downregulation of T-cell factor-1/Id2 (inhibitor of DNA binding 2) and cyclin D1, leading to G(1) phase elongation. Further assays with the TOPFLASH reporter and quantitative RT-PCR for other beta-catenin target genes such as Axin2 confirmed that overexpression of HDAC7 decreased beta-catenin activity. Knockdown of HDAC7 by lentiviral short hairpin RNA transfer induced beta-catenin nuclear translocation but downregulated cyclin D1, cyclin E1 and E2F2, causing HUVEC hypertrophy. Immunoprecipitation assay and mass spectrometry analysis revealed that HDAC7 directly binds to beta-catenin and forms a complex with 14-3-3 epsilon, zeta, and eta proteins. Vascular endothelial growth factor treatment induced HDAC7 degradation via PLCgamma-IP3K (phospholipase Cgamma-inositol-1,4,5-trisphosphate kinase) signal pathway and partially rescued HDAC7-mediated suppression of proliferation. Moreover, vascular endothelial growth factor stimulation suppressed the binding of HDAC7 with beta-catenin, disrupting the complex and releasing beta-catenin to translocate into the nucleus.

CONCLUSIONS

These findings demonstrate that HDAC7 interacts with beta-catenin keeping ECs in a low proliferation stage and provides a novel insight into the mechanism of HDAC7-mediated signal pathways leading to endothelial growth.

Plasma tissue inhibitor of metalloproteinase-1 and matrix metalloproteinase-9: novel indicators of left ventricular remodelling and prognosis after acute myocardial infarction

AIMS

Matrix metalloproteinase (MMP) activity is central to the development of left ventricular (LV) remodelling and dysfunction after acute myocardial infarction (AMI). We assessed the relationships with LV structure and function and outcome, of tissue inhibitors of metalloproteinase-1 (TIMP-1) and MMP-9, and compared with N-terminal pro-B-type natriuretic peptide (NTproBNP).

METHODS AND RESULTS

We studied 404 patients with AMI. Primary outcome measures were the associations of TIMP-1, MMP-9, and NTproBNP with death or heart failure, and with LV dimensions, function and remodelling (ΔLVEDV, change in LV end-diastolic volume between discharge and follow-up). Cut-off concentrations for prediction of death or heart failure were identified from receiver operator characteristic (ROC) curves. In multivariable analysis, TIMP-1 and NTproBNP had predictive value for LV ejection fraction pre-discharge (TIMP-1 P = 0.023; N-BNP P = 0.007) and at follow-up (TIMP-1 P = 0.001; N-BNP P = 0.003). MMP-9, TIMP-1, and NTproBNP correlated directly with LV volumes. MMP-9 (P = 0.005) and TIMP-1 (P = 0.036), but not NTproBNP, correlated with ΔLVEDV. For the combined endpoint of death or heart failure the area under the ROC curve was 0.640 for MMP-9, 0.799 for NTproBNP and 0.811 for TIMP-1. Patients with TIMP-1 > 135 ng/mL (P < 0.001) or NTproBNP >1472 fmol/mL (P < 0.001) had increased risk of endpoint. Consideration of both NTproBNP and TIMP-1 further improved risk stratification.

CONCLUSION

TIMP-1 and MMP-9 correlate with echocardiographic parameters of LV dysfunction and remodelling after AMI and may identify patients at risk of subsequent LV remodelling and adverse prognosis.

Circulating stromelysin-1 (MMP-3): a novel predictor of LV dysfunction, remodelling and all-cause mortality after acute myocardial infarction

INTRODUCTION

Changes to cardiac matrix are central to ventricular remodelling after acute MI and matrix metalloproteinase expression is implicated in this process. We investigated the temporal profile of MMP-3 and its relationship to LV dysfunction and prognosis following AMI.

METHODS

We studied 382 patients with AMI. Plasma MMP-3 was measured at 0-12, 12-24 h and for subsequent 24 h periods during admission. LV function (LVEF) was assessed by echocardiography pre-discharge and at a median of 148 days and clinical endpoints at a median of 313 days.

RESULTS

MMP-3 peaked prior to discharge thus pre-discharge levels were used in analyses. MMP-3 was associated with patient age (p<0.001), creatinine (p<0.001) and was higher in males (p<0.001) and hypertensives (p<0.001). MMP-3 inversely correlated with LVEF at follow-up (p=0.043), was higher in subjects with LVEF <40% (p=0.017) and in subjects with increasing EDV (p=0.017) or ESV (p=0.007) compared to those in whom volumes fell between visits. In the 58 patients reaching the endpoint of death or heart failure, MMP-3 was higher (p<0.001). On Kaplan-Meier analysis, subjects with levels above optimum cut off identified via ROC curves were more likely to suffer a clinical event (p=0.037).

CONCLUSION

MMP-3 is associated with left ventricular dysfunction, adverse left ventricular remodelling and prognosis after AMI.

Plasma matrix metalloproteinase-9 and left ventricular remodelling after acute myocardial infarction in man: a prospective cohort study

AIM

To describe temporal profiles of plasma matrix metalloproteinases (MMP-2 and MMP-9), and their relationship with echocardiographic (Echo) parameters of left ventricular (LV) function and remodelling, after acute myocardial infarction (AMI) in man.

METHODS AND RESULTS

Plasma MMP-2 and MMP-9 were assayed at intervals (0-12, 12-24, 24-48, 48-72, 72-96, and > 96 h) in 91 patients with AMI (ST-elevation/non-ST-elevation 77/24; 73% male; 40% anterior site) and on a single occasion in 172 age- and sex-matched control subjects with stable coronary artery disease. Echo assessment of LV volumes, LV ejection fraction (LVEF), and wall motion index score were assessed before discharge and at follow-up (median 176, range 138-262 days) for patients and on a single occassion in controls. Plasma MMP-2 was similar at all times after AMI, elevated when compared with control (P = 0.005-0.001) and unrelated to LV function or volume during index admission or at follow-up. Maximal MMP-9 was seen at 0-12 h and was elevated when compared with control (P = 0.002) followed by fall to a plateau. Both maximal and plateau MMP-9 concentration correlated with white blood cell (WBC, P = 0.023 to < 0.001) and neutrophil count (P = 0.014 to < 0.001). Maximal MMP-9 had independent predictive value for lower LVEF (P = 0.004) during admission and for greater change in LV end-diastolic volume between admission and follow-up (R = 0.3, P = 0.016). In contrast, higher plateau levels of MMP-9 were associated with relative preservation of LV function (increasing LVEF, P = 0.002; decreasing WMIS, P = 0.009) and less change in end-systolic volume and end-diastolic volumes after discharge (P = 0.001 and 0.024, respectively).

CONCLUSION

Both MMP-9 and MMP-2 are elevated following AMI. The biphasic profile of plasma MMP-9 is related to LV remodelling and function following AMI in man. Higher early levels of MMP-9 associate with the extent of LV remodelling and circulating WBC levels. In contrast, higher plateau levels later after AMI are associated with relative preservation of LV function. Temporal profile, rather than absolute magnitude, of MMP-9 activity appears to be important for LV remodelling after AMI.

Aortic aneurysms as a source of circulating interleukin-6

In keeping with the inflammatory paradigm of abdominal aortic aneurysm (AAA) pathophysiology, in vitro studies suggest that aneurysms secrete the proinflammatory cytokine interleukin-6 (IL-6). Circulating IL-6 levels are higher in patients with AAA with elevated circulating IL-6 an independent risk factor for cardiovascular mortality. To investigate whether aneurysms secrete IL-6 into the circulation, arterial IL-6 was measured from within the aorta in three groups of patients undergoing endovascular procedures; 27 AAA, 10 thoracic aneurysms (TA), and 15 controls. Overall, IL-6 was higher in the aneurysm groups (P < 0.0008) with significant rises corresponding to positions downstream to the aneurysm in both AAA and TA. There were no significant differences in IL-6 with aortic position in the control group. These data support the hypothesis that aneurysms secrete IL-6 into the circulation and may account for the high cardiovascular mortality observed in patients with aneurysms.

Matrix metalloproteinase-2: the forgotten enzyme in aneurysm pathogenesis

The pathogenesis of abdominal aortic aneurysm (AAAs) involves progressive cycles of proteolysis and inflammation, the product of proteolysis driving subsequent inflammation. Little is yet known about the initiating events. We review the specific literature examining the possibility that MMP-2 may be the initial catalyst. Histologically, elastolysis is one of the earliest observable events in aneurysm genesis. Matrix metalloproteinase-2 (MMP-2), as the dominant gelatinase differentially expressed in aneurysmal tissue and cells derived from aneurysms, would be a good candidate. We report the results of in vivo and in vitro experiments, which lend support to the importance of MMP-2 as an aneurysmal initiator.

Endothelial progenitor cells and abdominal aortic aneurysms

Endothelial progenitor cells (EPCs) are a population of circulating stem cells that hone in to sites of vascular injury where they undergo differentiation to become incorporated into damaged tissue. The aim of this study was to enumerate EPCs in patients with abdominal aortic aneurysms (AAA). CD133(+) peripheral blood mononuclear cells were immunomagnetically selected and CD34/CD133 was used as a marker of EPCs. EPCs were detected using flow cytometry. AAA patients had significantly higher levels of circulating EPCs than age-matched controls (2.43% vs. 1.25% of all events, P = 0.008). The role and function of EPCs in AAA remain to be determined, but their implication with angiogenesis may represent one plausible mechanism.

Circulating cytokines in patients with abdominal aortic aneurysms

Studies suggest that aneurysm-derived cytokines perpetuate the cycle of inflammation and proteolysis that is the pathological hallmark of abdominal aortic aneurysms (AAA). As interleukin (IL)-6 is an independent risk factor for cardiovascular mortality, such cytokines may also have important systemic effects. The purpose of this study was to investigate the effect of aneurysm repair on circulating levels of cytokines. Inflammatory cytokines were measured in 99 patients with AAA and 100 patients who had undergone AAA repair in the past. There was a significant reduction in IL-10 in the postoperative group, and a nonsignificant trend toward reduction in IL-6 and CRP in the postoperative group. Subgroup analysis of the postoperative group revealed significantly lower levels of IL-6 and CRP in the open group compared to endovascular aneurysm repair (EVAR). These results suggest that aneurysm repair may have an effect upon chronic levels of circulating inflammatory cytokines, and that the type of repair may exert some influence.

Effects of cell saver autologous blood transfusion on blood loss and homologous blood transfusion requirements in patients undergoing cardiac surgery on- versus off-cardiopulmonary bypass: a randomised trial

OBJECTIVE

Off-pump CABG is potentially associated with reduced intraoperative blood loss and homologous blood transfusion in comparison to on-pump CABG. In this randomised controlled study we investigated the effects of autologous cell saver blood transfusion on blood loss and homologous blood transfusion requirements in patients undergoing CABG on- versus off-CPB.

METHODS

Eighty patients were randomised into one of four groups: (A) on-CPB with cell saver blood transfusion (CSBT), (B) on-CPB without CSBT, (C) off-pump with CSBT and (D) off-pump without CSBT. Volume of intraoperative autologous blood transfusion, postoperative mediastinal blood loss and homologous blood transfusion requirements were measured. Homologous blood was transfused when haemoglobin concentration fell below 8 g/dl postoperatively. Pre- and postoperatively prothrombin time and partial thromboplastin time were measured.

RESULTS

Preoperative patient characteristics were well matched among the four groups. The amount of salvaged mediastinal blood available for autologous transfusion was significantly higher in the on-pump group (A) compared to the off-CPB group (C) (433+/-155 ml vs 271+/-144 ml, P=0.001). Volume of homologous blood transfusion was significantly higher in group B vs groups A, C and D (595+/-438 ml vs 179+/-214, 141+/-183 and 230+/-240 ml, respectively, P<0.005). The cell saver groups (A and C) received significantly less homologous blood than the groups without cell saver (160+/-197 ml vs 413+/-394 ml, respectively, P<0.005). Patients undergoing off-CPB surgery received significantly less homologous blood than those undergoing on-CPB CABG irrespective of cell saver blood transfusion (184+/-214 ml vs 382+/-397 ml, P<0.05). Postoperative blood loss was similar in the four groups (842+/-276, 1023+/-291, 869+/-286 and 903+/-315 ml in groups A to D, respectively, P>0.05). Clotting test results revealed no significant difference between the groups. There was no significant difference in postoperative morbidity between groups.

CONCLUSION

Off-pump CABG is associated with significant reduction in intraoperative mediastinal blood loss and homologous transfusion requirements. Autologous transfusion of salvaged washed mediastinal blood reduced homologous transfusion significantly in the on-CPB group. Cell saver caused no significant adverse impact on coagulation parameters in on- or off-CPB CABG. Postoperative morbidity and blood loss were not affected by the use of CPB or autologous blood transfusion. We recommend the use of autologous blood transfusion in both on- and off-pump CABG surgery.

Pharmacotherapy of abdominal aortic aneurysms

Aortic aneurysms account for 10,000 deaths annually in the UK, due to rupture. At present the only effective therapeutic strategy to treat abdominal aortic aneurysms is to surgically repair them; this carries an elective mortality of up to 10%. Recent advances in vascular biology have led to a greater understanding of the pathophysiological process that causes aortic aneurysms to expand and rupture. Key pathological processes include widespread aortic inflammation, proteolytic degradation of the extracellular matrix, neovascularisation and generation of reactive oxygen species. Identification of these processes has lead to pharmacological strategies to prevent aneurysm expansion and rupture. Many of these strategies have undergone proof of concept in animal models and some have now entered clinical trials. This review outlines current thinking regarding the molecular events leading to aneurysm expansion and explains how these processes may be inhibited. Experimental data on agents retarding aneurysm expansion in animal models are discussed. A significant proportion of the review details pharmacological agents that have undergone or are undergoing clinical trials. Pharmacological treatment for abdominal aneurysms is urgently required given the number of small aneurysms being diagnosed by screening programmes. This is a rapidly evolving field and one in which translation from experimental research to clinical practice is anticipated within 5 years.

A Review of Biological Factors Implicated in Abdominal Aortic Aneurysm Rupture

Abdominal aortic aneurysm (AAA) rupture is the 13th commonest cause of death in the Western World. Although considerable research has been applied to the aetiology and mechanism of aneurysm expansion, little is known about the mechanism of rupture. Aneurysm rupture was historically considered to be a simple physical process that occurred when the aortic wall could no longer contain the haemodynamic stress of the circulation. However, AAAs do not conform to the law of Laplace and there is growing evidence that aneurysm rupture involves a complex series of biological changes in the aortic wall. This paper reviews the available data on patient variables associated with aneurysm rupture and presents the evidence implicating biological factors in AAA rupture.

Characterisation of a myofibroblast-like cell line from an angiosarcoma

We have isolated a cell line (ASMM) by serial passage of cells from explant cultures of an angiosarcoma resected from the calf of a 62 year old female. ASMM has been in continuous culture for over eighteen months (>150 population doublings) and has a Fibroblast-like morphology with a doubling time of approximately 72 h. ASMM has a normal diploid karyology and is unable to generate tumors in nude mice or produce colonies in soft agar. Examination of the cytoskeletal proteins shows both desmin and vimentin and a low level of alpha-smooth muscle actin, which can be upregulated by treatment with TGF beta. Low levels of basal VCAM-1 are significantly upregulated with TNF alpha and reduced by the presence of TCF beta. Basal ICAM-1 is also upregulated with TNF alpha and we show an additional upregulation through TGF beta. ASMM expresses high levels of the hyaluronate receptor CD44, including the variant exons 6, 8 and 10. In addition, ASMM synthesises high levels of hyaluronate (HA), as did the original tumor. Unlike human umbilical vein endothelial cells (HUVECs) these cells were unable to generate capillary-like tubes when seeded onto basement membrane gels, and generated cords of cells containing many synthetic organelles and intermediate filaments. We were unable to detect the expression of factor VIII-related antigen, von Willebrand factor (vWF), CD31 or CD34, and were not able to induce expression of E-selectin after TNF alpha stimulation. In conclusion, this cell line represents a partially transformed population of cells which show characteristics consistent with myofibroblast-like cells. The production of high levels of HA and expression of CD44 may help to explain the high degree of agressiveness of the tumor from which ASMM was derived, as these molecules have been shown to play a role in cell motility and adhesion.